This happened to me also with PHP 5.4.1Copying the offending DLL everywhere didn't worket, and I don't have Postgres installed in the server, but also planned to use PHP against different Postgres versions, so the only solution I found that worked was to put in httpd.conf a line like this:LoadFile "C:/Program Files/PostgreSQL/8.4/bin/libpq.dll" but refering to the libpq.dll that comes bundled with PHP, like this:LoadFile "C:/php/libpq.dll" After that it worked fine to me.(c) https://stackoverflow.com/users/1373641/dayron-armas-peñafrom: https://stackoverflow.com/questions/551734/php-not-loading-php-pgsql-dll-on-windows/10439560#10439560